1. Field of the Invention
The present invention relates to a polarizer for converting incident light beam into a linear polarization beam and an optical device using the polarizer.
2. Description of Related Art
Conventionally, a projector having a light source, an electric optical device for modulating the light beam irradiated by the light source in accordance with image information, and a projection optical system for enlarging and projecting the light beam modulated by the electric optical device has been used as an optical device using the electric optical device.
Liquid crystal device is known as the electric optical device, which includes an electric optical element having a pair of transparent substrates between which electric optical material such as liquid crystal is sealed and enclosed, and two polarization plates as a polarizer disposed on the light-incident side and light-emission side of the electric optical device.
In a conventional arrangement, the polarizer is made of organic material such as PVA (polyvinyl alcohol) including iodine and colorant, which is made by sandwiching a film oriented in a predetermined direction with a support body such as glass plate or by adhering the film to the support body.
However, since such conventional polarizer is made of organic material, the polarizer is weak against high temperature and is decolorized after continuous use in an environment of more than 70° C. to lose polarizing function.
Accordingly, a structural birefringent polarizer has been proposed as a polarizer made of inorganic material. The structural birefringent polarizer is constructed by forming a birefringent portion where a plurality of stripe-shaped minute linear convex treads of metal such as aluminum are arranged on a surface of a transparent substrate such as glass, which uses diffraction of the space between the convex treads to convert the incident light beam to the linear polarization beam.
However, since such structural birefringent polarizer absorbs a part of the incident light beam on the birefringent portion, the glass substrate is distorted on account of heat, thus failing to conduct appropriate polarization conversion. Especially, when the glass substrate is disposed on the light emission-side, the polarization axis of the polarized light beam converted by the birefringent portion is revolved in the glass substrate, thereby causing light transmission failure where a part of the light does not pass through the glass substrate.